Even for a 12-year-old watching the tape-delayed 1960 Rome Olympics on television and seeing Cassius Clay winning a gold medal in boxing, it was obvious.

He was thrilling. Different. Even a kid could see it: the compelling combination of speed and power, and throw in courage and grace and humor and pride and militancy and bombast and poetry, too, perhaps presaging by decades the hip-hop era. Baby boomers who paid attention to boxing instantly became lifelong aficionados, following his career for the next 20 years as he soon became like nothing in sports before or since.

Yes, he transcended sports, as we’ve been reminded since his death last week at the age of 74. But it’s important to remember he first made his mark as a world-class athlete. A boxer. A fighter. And within his greatness as a fighter, there were enough metaphorical slips, clinches and low blows to make him a hero in a truly classic sense: flawed. In his case, intriguingly so.

Clowning around against Henry Cooper in 1963, winking at Elizabeth Taylor at ringside, he suddenly found himself on his butt, disoriented, never having seen a left hook to the jaw in the final seconds of the fourth round. He survived, and won by TKO in the fifth, but the near-knockout by an inferior opponent nearly derailed his destiny.

Then, in 1964, after the fourth round of his championship challenge to Sonny Liston, he told trainer Angelo Dundee to cut off his gloves. He wanted to quit because of blurred vision from an astringent substance intentionally or accidentally placed on Liston’s gloves. Dundee wouldn’t let him quit, washed out his eyes, and Clay became champion when a beaten and demoralized Liston wouldn’t answer the bell for the seventh round. The next day Clay announced his new name: Muhammad Ali. But imagine if he, instead of Liston, had lost while sitting on his stool.

In the rematch with Liston in 1965, Ali failed to go to a neutral corner after scoring a first-round knockdown. The fight turned into a farce, and the farce turned into suspicions of a fix that remain to this day. Although the famous photo from that bout, with Ali standing over and berating a prone Liston, has become an iconic celebratory image, the actual behavior caught by the camera is a reminder that Ali’s hero growing up wasn’t Joe Louis or Jackie Robinson but a fat white pro wrestler named Gorgeous George, whose schtick was to promote his own celebrity, skirt rules and violate standards of sportsmanship.

Also in 1965, he fought Floyd Patterson, a popular former champion who just wasn’t physically in Ali’s class. Ali tortured and humiliated Patterson for 12 rounds instead of ending it as soon as possible. It was hard to watch, even harder to excuse. He gave a repeat performance, and added three more rounds, against Ernie Terrell in 1967. It was a viciously ugly side to Ali, there for all the world to see.

Ali’s first loss, in 1971, in his first fight against Joe Frazier, turned out to be a crucible through which he emerged tougher, eventually twice regaining the heavyweight title. The loss to Frazier perhaps did more to sow seeds of future greatness than a victory might have. He was rushed into that fight, his third in a 4½-month span after a 3½-year exile for refusing induction into the Army.

Frazier was undefeated, ferocious, relentless. Yet Ali was splendid in the first six rounds, hitting Frazier with punches that would have dropped a lesser foe. It was a 15-round classic. Both combatants would be hospitalized immediately after Frazier won a unanimous decision, after Ali took everything Frazier had to give, including a stunning knockdown in the final round, from which Ali rose after a few seconds and finished on his feet, still giving and taking punches.

But even though there was greater glory for Ali after that defeat — two victories against Frazier, and the sensational knockout of George Foreman, and the victories against Ken Norton and Ron Lyle and Jimmy Young and so many others — there were, still, inglorious missteps.

There was Ali’s persistent, clueless, hurtful verbal attacks on Frazier, calling his most worthy opponent a gorilla during the lead-up to their third fight, what was to be the 1975 epic “Thrilla in Manila.”

There was the ill-advised 1976 “mixed-rules” contest against Japanese wrestler Antonio Inoki, an embarrassing extravaganza in which Ali threw fewer than 10 punches and in exchange suffered cuts and bruises on his legs and, more seriously, blood clots, after having been kicked for 15 rounds.

And there was his lethargic performance in a 1978 loss to the poorly regarded Leon Spinks, who was fighting professionally for only the eighth time. The generous split decision fails to inform how lopsided the fight was in Spinks’ favor.

Through all that, though, aficionados of Ali remained loyal. His flaws made him human, and therefore his remarkable boxing achievements made him even more authentically heroic.

In the end, it shouldn’t be the pose of braggadocio struck over a hapless Sonny Liston that remains as the iconic Muhammad Ali image. It should be the Sports Illustrated cover photo in March of 1971 showing a brave and skilled and noble Ali falling backward toward the canvas after getting hit with Joe Frazier’s absolute best punch in the final round of an already lost cause. It’s the wrongheadedness of the accompanying headline — “End of the Ali Legend” — that screams with irony, for that was in fact the beginning of the legend’s renewal and exponential growth. It’s the knowledge that Ali got up immediately when lesser mortals would have stayed down. It’s the knowledge that Ali finished proudly, defiantly, on his feet, fighting.

It’s the knowledge he took that defeat and then, against all odds, gave us a sensational second act of a unique sports career.